1. Field of Invention
The present invention relates to a vehicular anti-lock control system that includes anti-lock control means for suppressing locking of a wheel by controlling fluid pressure supplied to a wheel brake based on a reference fluid pressure when it is determined, based on a wheel speed detected by a wheel speed sensor, that the wheel has a tendency to lock.
2. Description of Related Art
Japanese Patent Publication No. 3382269 discloses a vehicular anti-lock control system wherein when a wheel is about to lock due to an excessive braking force of a fluid pressure type wheel brake, fluid pressure supplied to the wheel brake is reduced to suppress locking of the wheel. In this system, when starting anti-lock control, a reference fluid pressure as a reference for proportional-integral-derivative (PID) feedback control of the fluid pressure supplied to the wheel brake is obtained by correcting an actual fluid pressure when starting the anti-lock control with a wheel acceleration/deceleration. After the anti-lock control is started, the reference fluid pressure obtained when the control is started is corrected corresponding to the tendency of the wheel to lock and is used for the PID feedback control.
However, in this conventional system, the road surface friction coefficient is not taken into consideration when the reference fluid pressure for anti-lock control is changed. Therefore, even in the case, for example, where the amount of decrease of the fluid pressure could be made small since the road surface friction coefficient is sufficiently large, an excessive pressure decrease may be carried out, so that the braking distance might not be sufficiently reduced or the braking feel might be deteriorated.